manual/include/whats-in-a-session.html

<p>
  The <dfn>Session</dfn> is the fundamental document type that is created and
  modified by the Ardour workstation.  A Session is a folder on a computer
  filesystem that contains all the items that pertain to a particular project
  or "recording/editing/mixing session".
</p>
<p>
  The Session folder includes these files and folders:
</p>
<ul>
  <li><code><em>session_name</em>.ardour</code> the main session snapshot</li>
  <li><code>*.ardour</code>, any additional snapshots </li>
  <li><code><em>session_name</em>.ardour.bak</code>, the auto-backup snapshot</li>
  <li><code><em>session_name</em>.history</code>, the undo history for the session </li>
  <li><code>instant.xml</code>, which records the last-used  zoom scale and other metadata</li>
  <li><code>interchange/</code>, a folder which holds the raw audio and MIDI
  files (whether imported or recorded)</li>
  <li><code>export/</code>, a folder which contains any files created by the
  <kbd class="menu">Session &gt; Export</kbd> function</li>
  <li><code>peaks/</code>, a folder which contains waveform renderings of
  all audio files in the session</li>
  <li><code>analysis/</code>, a folder which contains transient and pitch
  information of each audio file that has been analysed</li>
  <li><code>dead sounds/</code>, a folder which contains sound files which
  Ardour has detected are no longer used in the session (during a <kbd
  class="menu">Session &gt; Clean-up &gt; Clean-up Unused Sources</kbd>
  operation, will be purged by <kbd class="menu">Flush Waste Basket</kbd>, see
  <a href="@@cleaning-up-sessions">Cleaning Up Sessions</a>)</li>
</ul>
<p>
  A session combines some setup information (such as audio and MIDI routing,
  musical tempo &amp; meter, timecode synchronization, etc.) with one or more
  Tracks and Buses, and all the Regions and Plug-Ins they contain.
</p>

<p>
  Ardour supports loading session files created with older versions of the
  program. The oldest known version is 2.8 released in 2009. With very few 
  exceptions, Ardour will load all session data from such files. The data that 
  cannot be supported (e.g. the old way of storing region fades) will be
  skipped entirely.
</p>